Ensure there is a key control and accountability system in place. In particular ensure keys are kept in a secure location and there are records of who has each key. There are key cabinets and key control software that specialise in this.
Carry out annual maintenance on locks and other door hardware. The best security system falls down very quickly if a door closer isn’t latching the door shut for example, or the lock is not configured correctly in how the door handles on each side are supposed to work.
Ensure all Fire and Exit doors are compliant with recent legislation. The legislation is very specific about how these doors should function and it is critical that they are maintained in accordance with requirements.
Eradicate poor crime prevention behaviours or procedures. So for example rear doors being used for shortcuts, or doors wedged open by employees to make it easier for them to access for a cigarette. As with poor maintenance, poor behaviours can easily render a security system inadequate. Affordable stand alone kits are available to alert if the door is left open for too long (similar to fridge door).
Electronic access systems (swipe cards) not only provide a very high security system, but they also provide a full audit trail of access to and from any particular areas.
Keep abreast of new technology which may benefit your business, on either of a security or efficiency basis. For example wireless access systems such as Salto and Clay allow you to unlock or lock all doors instantly from anywhere in the world using an app. Similarly, Videofied is a wireless remote monitoring system that easily allows to you monitor multiple locations without the need to run cabling.